This invention relates in general to passenger seat belt devices and in particular to a new and useful winding attachment for passenger safety belts in vehicles which produce a retightening of the belt during emergency conditions.
Retighteners serve to eliminate a slack in the belt in a collision by retracting the belt so that the free prolapse path or period until the belt becomes effective is as small as possible. Orderly belt retightening requires a belt retraction of about 20 cm. This corresponds to a rotation of the belt strap stool of about 550.degree. . (DE-AS No. 25 10 514).
In DE-AS No. 25 10 514, which corresponds to U.S. Pat. No. 4,014,479, two rotating wings are arranged axially side by side on a rotary piston shaft of a rotary piston engine, where a wing fixed on the case is assigned to the first rotating wing on the rotary piston shaft, forming a first expansion chamber, while a rotating wing arranged non-rotationally on a rotating jacket is assigned to the second rotating wing on the rotary piston shaft, forming a second expansion chamber. The driver clutch over which the rotary piston engine drives the belt strap spool is formed by a plurality of circumferential bores in the side disc of the belt strap spool facing the rotary piston engine, into which can be inserted a bolt admitted by the propellant gases, which is arranged on the jacket provided with the rotating wing. The belt strap spool is to this end rotatably mounted on a journal fixed in the case. For blocking the automatic takeup roller, the side disc of the belt strap spool facing the rotary piston engine is designed as a ratchet wheel, which cooperates with a ratchet. The gases entering the two expansion chambers cause then a rotation of the rotating wing of the rotary piston shaft, which cooperates with the fixed wing. It also causes a rotation of the second rotating wing of the rotary piston shaft, which cooperates with the rotating wing on the jacket. At the same time the expansion chamber widens between the second rotating wing of the rotary piston shaft and the rotating wing on the jacket, so that the latter imparts almost two revolutions to the belt strap stool.
A disadvantage of the known winding attachment is, however, that due to the numerous differences of the automatic takeup roller relative to the existing series-produced, that is, technically refined automatic takeup roller, which is relatively inexpensive due to its larger quantities, subsequent attachment of the belt tighteners on the latter is not possible.
Beyond that the pressure of the propellant gases acts during the expansion also on the rotary piston shaft, so that the latter is loaded radially away from the expansion chamber enclosing the propellant gases. This radial load requires a solid design of the rotary piston shaft and an elaborate support.